Open center vs. close center

[Groo]

any good primers out there discussing the pros and cons of each system?
Open center = fixed displacement (for the most part) and closed center = variable displacement.

What is there beyond that? What can closed center do that open centered can't? Anything else out there?

 

[bigdeano]

Google would give you lots of reading material. Aircraft have always used closed center. You only need a pipe big enough for the flow required by each component, not the entire pump flow, so it saves a lot of weight. Also you can operate more than one control at the same time. Important if you don't want to crash.

 

[JD5210]

These youtube videos maybe more than you are looking for. I found them to be every informative

Hydraulics Math - YouTube

 

[/pine]

With a closed center system pressure lines can be tee'd

I have a Ditch Witch 3610 and it has both open and closed center systems...

 

[chevy791979]

Closed center is far more fuel efficient and heat efficient. It only uses what oil it is told to move by the pilot oil input from the operator. And flow adjustability with L/S pump is good for motors and such that require a certain flow to work safely.

 

[majorwager]

Chevy is exactly correct. Heat is the issue, very destructive. I have a older IH tractor, open center, and the hyd operating temp pushes the boundaries even if no oil is feeding a motor or cylinder. It is very rare to find closed center systems in sub-100 hp tractors.

 

[Tx Jim]

Closed center is far more fuel efficient and heat efficient.

Closed center hyd system that develops a high pressure internal leak can have heating problems. More fuel efficiency is determined by number of hyd functions that are performed. My guess is a 50 or 55 series JD tractor hyd pump is out of stroke for a very limited amount of time. Then when operating a hyd motor it never goes out of stroke.

 

[chevy791979]

Closed center hyd system that develops a high pressure internal leak can have heating problems. More fuel efficiency is determined by number of hyd functions that are performed. My guess is a 50 or 55 series JD tractor hyd pump is out of stroke for a very limited amount of time. Then when operating a hyd motor it never goes out of stroke.

Internal leaks are considered a malfunction.

I will have to disagree with you on the fuel efficient statement. If you took 10 circuits for both types and both running all hyd motors a closed center will out perform an open center all day long. You can tune a closed center to match needed flow. The open center is all or nothing.

 

[Tx Jim]

Internal leaks are considered a malfunction.

I will have to disagree with you on the fuel efficient statement. If you took 10 circuits for both types and both running all hyd motors a closed center will out perform an open center all day long. You can tune a closed center to match needed flow. The open center is all or nothing.

Have you ever operated an orbit motor on a JD CC hyd system? Evidently not.

 

[chevy791979]

Have you ever operated an orbit motor on a JD CC hyd system? Evidently not.

Once or twice

 

[chevy791979]

On the pump never going out of stroke comment, that would be true on a motor requiring 35GPM with a pump output of 38+/-. What is nice with cc is you can have a pump capable of 3x the needed flow. But like stated before, most CC systems are not under100hp

 

[chevy791979]

Have you ever operated an orbit motor on a JD CC hyd system? Evidently not.

Orbit motor? Are you referring to a travel motor? As far as I know all hyd motors are used in a rotation function

 

[gary49]

I don't know much about this topic, but there are lots of long nose John Deeres that are closed center and under 100 hp. Our 2155 has 55 engine hp and the loader operation is smooth as glass and powerful. Have no complaints at all about the hydraulics on that tractor.

 

[chevy791979]

I don't know much about this topic, but there are lots of long nose John Deeres that are closed center and under 100 hp. Our 2155 has 55 engine hp and the loader operation is smooth as glass and powerful. Have no complaints at all about the hydraulics on that tractor.

True ..... I'm a construction guy so don't do a whole lot on the small green ones

 

[majorwager]

Gary, my error.

Many deere 50-60 series tractors, even lower hp models were closed center. These were from early 1990's perhaps some from late 80's.

Fast fordward to 21 century, hard pressed to find a AG tractor <100 hp with closed center hyd. Exclude some speciality Models NOT designed for AG row crop or utility chores. Regret my generalized characterization.

 

[Tx Jim]

Gary, my error.

Many deere 50-60 series tractors, even lower hp models were closed center. These were from early 1990's perhaps some from late 80's.

Fast fordward to 21 century, hard pressed to find a AG tractor <100 hp with closed center hyd. Exclude some speciality Models NOT designed for AG row crop or utility chores. Regret my generalized characterization.

JD 20-55 series utility tractors built from '65-'92 with hp ranges from 38 pto to about 100 pto all had CC hyd's with a few exceptions such as models 830 & 2040 with 3 cyl engines that had OC hyd's

 

[Tx Jim]

Orbit motor? Are you referring to a travel motor? As far as I know all hyd motors are used in a rotation function

Sorry I have no clue what a "travel motor" is. Below is a photo of orbit motor.

 

[chevy791979]

All motors are an orbit rotation. Aka they all turn as fast as they "told" to via flow. A travel motor is a motor that turns a tire or final drive gear box.

 

[Tx Jim]

All motors are an orbit rotation. Aka they all turn as fast as they "told" to via flow. A travel motor is a motor that turns a tire or final drive gear box.

So is a travel motor hyd powered?

 

[chevy791979]

Yes. It's the same ( can be ) as what you showed. But they can get more complicated than a fixed displacement one like you showed. I deal with alot of this type.